The effect of casting solvent on the material properties of poly(γ-methyl-D-glutamate)

The effect of casting solvent on the material properties of poly(γ-methyl-D -glutamate), PMDG, was investigated. The specific solvents used were chloroform, trifluoroacetic acid, dichloroacetic acid, methylene chloride, hexafluoroisopropanol, and tetrachloroethane. The different nature of these solvents controlled the degree of α, β, or random coil contents of the final film. The effect of the morphology on material properties induced by the respective solvents was investigated by dynamic mechanical measurements of the dry films, stress strain behavior of both wet and dry films as well as by wide-angle x-ray diffraction, small-angle light scattering, and optical microscopy. Infrared spectroscopy was used to help determine α or β content. It was found that the casting solvent has considerable influence on material behavior and morphology. These differences are reflected in both the dynamical mechanical (small strain) and stress–strain (large strain) measurements as well as the x-ray scattering and optical microscopy. It was noted by light scattering that all films gave rise to anisotropic rod scattering with the exception of the β film cast from trifluoroacetic acid. This latter film appeared to be optically isotropic.     

Structural studies of single spherulites and partially spherulitic films of poly(methyl-D-glutamate)

Isolated spherulites of poly(methyl D -glutamate) (PMDG) were nucleated in bromoform. The morphology of these spherulites was investigated by SEM and photographic small-angle light scattering (SALS). From the SALS patterns, the development and growth of the spherulites could be noted. Films of PMDG cast from bromoform solution were found to be partially spherulitic. The mechanical properties of these films, prepared by different procedures, were compared with the general behavior of PMDG films cast from chloroform, the latter of which does not contain spherulitic texture.     

Preparation and structure-property studies on copolypeptides of γ-methyl glutamate-glutamic acid and γ-methyl glutamate–γ-benzyl glutamate

A series of copolypeptides of poly(methyl glutamate-glutamic acid) (PBC) and poly(methyl benzyl glutamate) (PMB) were prepared from homopolymeric poly(methyl D-glutamate) (PMDG) via a variety of synthetic routes. Following their characterization, these copolymers were then investigated via dynamic mechanical spectroscopy, stress-strain analysis (wet and dry), and wide-angle x-ray scattering (WAXS). It was found that the copolymers could be prepared from homopolymeric PMDG with minimal chain degradation or side reactions. The mechanical properties of either series did not follow a simple trend, in that specific properties such as Young's modulus went through either a maximum or minimum with composition ratio of the two comonomers. based on the WAXS studies, some rationalization for this behavior was established. Specifically, the nature of the side-chain interaction, and therefore chain packing, was strongly affected by comonomer ratio.